The present invention relates to a thin film semiconductor device having thin film transistors (hereinafter, referred to as TFT) and capacitive elements provided on the same substrate, to a method of manufacturing thereof, to an electro-optical device using the thin film semiconductor device as a substrate for the electro-optical device, and to an electronic apparatus having the electro-optical device. More specifically, the present invention relates to a technology of manufacturing a capacitive element having a high capacitance.
In the case of manufacturing a thin film transistor device having TFTs and capacitive elements provided on the same substrate, when a semiconductor layer coplanar with the TFT semiconductor layer is made be conducted to form an electrode, an insulating layer coplanar with a gate insulating layer is used to form a dielectric layer, and a conductive layer coplanar with a gate electrode is used to form an upper electrode, the TFT and the capacitive elements can be provided through the reduced number of processes. This arrangement has been widely used in a device substrate of a liquid crystal device (electro-optical device) that uses TFT as a nonlinear device for switching devices, and various thin film semiconductor devices.
However, for the capacitive element, when the dielectric layer becomes thinner, a larger electrostatic capacitance can be obtained, whereas for the TFT, when the gate insulating layer becomes thinner, the electric strength is reduced. Thus, an arrangement in which the insulating layer formed at the same time with the dielectric layer is thinned to form the dielectric layer, for the capacitive element, is disclosed (for example, refer to Japanese Unexamined Patent Application Publication No. 6-130413)
However, when the thickness of a dielectric layer of the capacitive element and the thickness of the gate insulating layer of the TFT are different from each other, a mask should be added in order to make the dielectric layer of the capacitive element be thinner by etching. For this reason, it is necessary to add each of a mask formation process and a mask removal process. Therefore, there is a problem in that productivity is lowered.